Charge and wavelength scaling of RF photoinjectors: a design tool

The optimum design of an emittance compensated RF field photoinjector is very complicated and time-consuming, relying heavily on multi-particle simulations without good analytical models as a guide. Emittance compensated designs which have been developed, however, can be used to generate other designs with no additional effort if the original design is scaled correctly. This paper examines the scaling of RF photoinjector design with respect to charge and wavelength, and presents emittance and brightness scaling laws for these variables. Parametric simulation studies are presented to illustrate these scaling laws. A practical design for the TESLA FEL RF photo-injector is developed using these scaling techniques